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Simon, Ulrich; Flesch, U.

doi:10.1023/a:1009637102831

Cited by 62 publications

(50 citation statements)

References 11 publications

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“…Figure S3 shows M" data from a pressed pellet of Na-X with sputtered gold contacts, recorded at 303 K. An intense peak at high frequency is clearly seen, which has been previously attributed to the local motion of a sodium ion within the large α cages in zeolite X. 6 The peak (or hump, rather) at low frequency, however is not well resolved from the large high frequency peak, as in references 4 and 6. This was troubling at first, but further experimentation revealed the answer.…”

Section: S1)mentioning

confidence: 76%

“…6 Interestingly, VPI-9 samples do not show multiple peaks at any temperature in the M" spectra when powder samples are sandwiched between Pt plates, suggesting the absence of internal relaxation processes.…”

Section: S1)mentioning

confidence: 97%

“…Figure S4 shows M" spectra of Na-X powder, held between two platinum discs in vacuum, at various temperatures, and in this case two well resolved peaks are observed. The low frequency peak has been attributed to the long range ionic conduction process 6 , but the full interpretation is more complex, and will be discussed shortly. Finally, Figure S5 shows M" data for Na-X powder dropcast from an ethanol slurry onto an interdigitated electrode (IE) structure (Novocontrol).…”

Section: S1)mentioning

confidence: 99%

“…In a series of papers on ionic motion in zeolites [3][4][5][6] , it was suggested the presentation of data in the modulus representation, equation 1, and in particular the imaginary part of the modulus, M" as a function of frequency, rather than traditional impedance (Z) data, allowed for more straight forward visualization of ionic conduction and local relaxations. In equation S1, i is the square root of -1, ω is the frequency in radians per second, C 0 is the empty cell capacitance, M* is the complex modulus, and Z* is the complex impedance.…”

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confidence: 99%

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Conductivity of Mono- and Divalent Cations in the Microporous Zincosilicate VPI-9

McKeen

Davis

2009

J. Phys. Chem. C

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Impedance spectroscopy is used to investigate the long-range ionic conductivity of the microporous, zincosilicate VPI-9 (Si/Zn ) 4.0) (International Zeolite Association framework type VNI) containing the alkali cations Li + , Na + , K + , Rb + , and Cs + , and the alkaline earth cations Mg 2+ , Ca 2+ , and Sr 2+ . Monovalent cation-exchanged samples Li-and Na-VPI-9 lose X-ray crystallinity upon vacuum dehydration at 450 °C, whereas K-, Rb-, and Cs-VPI-9 remain crystalline and exhibit conductivities of 1.7 × 10 -4 , 3.5 × 10 -4 , and 4.9 × 10 -4 S/cm, respectively, at 450 °C and activation energies of 0.72, 0.64, and 0.69 eV, respectively, in the temperature range 150-450 °C. Divalent cation-exchanged sample Mg-VPI-9 also loses X-ray crystallinity, but Ca-and Sr-VPI-9 remain crystalline and exhibit conductivities of 2.3 × 10 -6 S/cm and 7.7 × 10 -7 S/cm, respectively, at 450 °C, and activation energies of 0.88 and 0.91 eV, respectively, over the temperature range 150-450 °C. When compared to aluminosilicate zeolite X (Si/Al ) 1.25) exchanged with the same cations, all crystalline M-VPI-9 materials have greater conductivities than M-X, with the exception of K-X (1.6 × 10 -3 S/cm at 450 °C), with the greatest differences arising between the divalent exchanged materials. Dense, crystalline zincosilicate samples with the compositions K 2 ZnSi x O 2(x+1) (x ) 2-5), Rb 2 ZnSi 5 O 12 , and Cs 2 ZnSi 5 O 12 are also prepared and characterized for comparison with the microporous materials and exhibit much lower conductivities than their microporous counterparts at the same composition.

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Section: S1)mentioning

confidence: 76%

Section: S1)mentioning

confidence: 97%

Section: S1)mentioning

confidence: 99%

mentioning

confidence: 99%

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Conductivity of Mono- and Divalent Cations in the Microporous Zincosilicate VPI-9

McKeen

Davis

2009

J. Phys. Chem. C

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“…This is based on the presence of partially occupied edge-sharing [LiO 4 ]-tetrahedra within densely packed Li 2 O-layers where Li cations can find shorter pathways for charge transportation (about 2.5 Å ) [6]. This feature is unusual in known Libearing zeolites [8][9][10]. Most Li-exchanged microporous materials contain only extra-framework Li cations far apart from each other in porous cages and channels.…”

Section: Introductionmentioning

confidence: 99%

Lithium dynamics in the zeolite-like lithosilicate RUB-29 and its high-temperature structure after dehydration (Cs14Li42Si72O172)

Park

Parise

Franke

et al. 2008

Microporous and Mesoporous Materials

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The thermally induced modifications of the zeolite-like lithosilicate In particular, extra-framework Li cations located within porous 8-and 10-membered ring-channels, where these Li cations were partially coordinated with zeolitic water in the original structure, migrate into densely packed Li 2 O-layers after dehydration. As a result of the migration, the number of empty sites relevant for Li hopping in Li 2 O-layers decreases, which give a negative effect on the long-range charge transfer in dehydrated RUB-29. Its DC conductivity values estimated from AC impedance spectra lie between 2 · 10 À5 and 6 · 10 À5 S cm À1 at 873 K, and a low activation energy of 51 kJ/mol (ffi 0.53 eV) could be determined for the bulk charge transfer process in dehydrated RUB-29.Li

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